This invention relates to a curved guide for paternoster-type document carriers, each carrier being connected with the aid of a support arm rotatably articulated on each front side to an endlessly moving chain and each carrier being conducted by means of a bent lever attached to each front side of each carrier in an inverted V-shaped position with the aid of guide rollers provided at the lever ends and running in slotted guideways which intersect at the two deflection points.
A curved guide of this type is already known, for example, from German patent specification No. 1,436,231. The paternoster-type document carriers include a rotatably mounted support arm on each front side articulating with the pivot pin which supports the respectively associated bent lever in a non-rotatable fashion. Said rotatably mounted support arm is connected via a joint with the endless driven chain. Each support arm is extended beyond said joint, the extension having an inverted T-shaped configuration. The flanges of the extension are perpendicular to the longitudinal direction of the support arm and are provided at their free ends with a guide roller (or caster) which move in succession in the direction of motion in a special slotted guideway extending between the chain segments. Such an arrangement and guide system for the carriers subjects the chain only to the carried weight and excludes any and all derailing and outwardly directed forces, thus ensuring reliable and low-noise operation of the registry equipped with paternoster-type carriers.
In particular when the paternoster-type carriers are operated at higher speeds, it has been found that, due to the increased accelerations and decelerations occurring at the sites of deflection, a certain amount of rough or bumpy operation results in the carriers which pass through these deflection sites and which, in addition, carry very different loads. The first cause of such bumpy operation is due to the fact that the centers of the pivotal axis for the guide wheel, the support arms of the next successive carrier and one arm of the bent levers firmly secured to the associated pivot pin of the carrier together form a straight line, thereby producing a knee lever on the front side of each carrier which is suddenly pushed through due to the concomitant pull of the support arm as the chain continues to run. A certain amount of swaying and pendulous oscillation of the respective carrier is caused because the outer guide roller (or caster) located on the afore-mentioned straight line has no guidance in such a position in the direction of the pendulous movement of the carrier at the moment this knee lever is formed and because the inner guide roller of the other bent lever has a certain amount of play in its slotted guideway, just like the outer guide roller.
The bumpy operation of the carriers caused at the site of deflection for a number of reasons in conjunction with a certain amount of deformation or buckling capacity has resulted in the following situation: in the intersection the leading guide roller of a bent lever has entered the wrong slotted guideway, thereby twisting the carrier which is formed, for example, by a frame to receiving hanging or other suspended files in a corkscrew-like configuration resulting in considerable damage to the document containers. In particular, such incidents result in annoying interruptions of operation and high repair costs.
The carriers, however, could be designated to be so stable as to eliminate any possibility of their being twisted or deformed. In view of the relatively long length of these carriers, however, such a step would increase the inherent weight of the carriers to such an extent that they would become uneconomical to manufacture, particularly since this would also entail the necessity of reinforcing other structural parts of the moving registry.
The object of the instant invention is therefore to further develop the known curved guide for paternoster-type document carriers using the other features already mentioned in the first paragraph at the outset in such a way that the guide rollers of each bent lever secured to a carrier can be reliably moved in the intersection into the associated slotted guideway by employing simple and economically feasible measures while retaining the document carriers known hitherto.